"Someone who I know knows him and he asked to have my number and then he texted me," she recounted. "I was like 'Oh my gosh, this is so weird!' but then I never texted him back because I found the love of my life."

Klum said she thought it was better to not respond than say no.

"Like, what do you say? You want to go out? And I'm like, no. It's better not to say anything," she said. "I'm embarrassed about it."

Klum met Kaulitz at a friend's birthday party in February the night of her previous appearance on Ellen.

"That was the day when actually I didn't want to go out at all," the star recalled. "I came home at night and it was my friend's birthday and he said, please come. So I got ready again and put my heels on and went to the birthday party and there [Kaulitz] was."

"It was to the point so bad that I couldn't even look at him. You know when you're immediately attracted to someone where you're like, oh my gosh, I can't look at him," she said.

Klum and Kaulitz made their red carpet debut as a couple at the amfAR Cinema Against AIDS gala during the Cannes International Film Festival in May. The model shared a kiss photo with Kaulitz on Sunday.

"I miss you," she wrote in German.

Klum and Project Runway co-star Tim Gunn announced last week they are leaving the show for a new Amazon series. The pair will develop, produce and star in the new fashion reality show.